The idea that dendrimers may function as robust, covalently bonded, and surface enclosed nanoscopic encapsulators for smaller moieties including organic molecules and inorganic ions, has attracted considerable attention. Based on results from dilute solution viscometry of poly(amidoamine) (PAMAM) dendrimers, it was hypothesized by D. A. Tomalia et al in the Journal of the American Chemical Society, Volume 109, Pages 1601-1603, (1987), that the intramolecular density of dendrimers with symmetrical branch cells should decrease with the radial distance from the core until a minimum is reached at certain generations above which the trend would reverse, and that the intramolecular dendrimer density would start increasing with the dendrimer radius in outer layers of these macromolecules.
Subsequent experiments with various dendrimers revealed that this hypothesis may have been accurate, and that dendrimers may in fact be globular nanoscopic entities of (i) relatively soft and spongy interiors capable of hosting smaller guest molecules, and (ii) a dense outer shell penetrable for small molecules such as solvents or classical organic and/or inorganic reagents but impenetrable to large molecules such as high molecular weight macromolecules, other dendrimers, or their parts; i.e., P. R. Dvornic et al, Polymeric Materials Science & Engineering, Volume 77, Pages 116-117, (1997).
For example, it was shown that poly(amidoamine) dendrimers can encapsulate Cu.sup.2+ cations by complexing the cations into the interior depending upon the pH, i.e., M. F. Ottaviani et al, in the Journal of the American Chemical Society, Volume 116, Pages 661-671, (1994); and that after modification of the dendrimer surface by hydrophobes, these complexes become soluble in organic solvents such as toluene, whereas Cu.sup.2+ cations are otherwise not soluble, i.e., Y. Sayed-Sweet et al, Journal of Materials Chemistry, Volume 7(7), Pages 1199-1205, (1997).
It has also been shown that (i) poly(propyleneimine) (PPI) dendrimers may function as molecular boxes for smaller organic molecules such as dyes and radicals, i.e., J. F. G. A. Jansen et al, in Science, Volume 266, Pages 1226-1229, (1994); that (ii) so-called arborols may be rendered chemically reactive to bind in their interior other reagents such as o-carborane delivered from their exterior, i.e., G. R. Newkome et al, in Angew. Chem. Int. Ed. Engl., Volume 33, Pages 666-668, (1994); and that (iii) PAMAM dendrimers may serve as inert, confined, nanoscopic reactors, for polymerization reactions if both the monomer or monomers and the initiator are delivered into and enclosed within their interiors, i.e., V. U. Wege et al, in Polymer Preprints, Volume 36, Number 2, Pages 239-240, (1995).
However, these references refer to results obtained using exclusively pure dendrimers. There have been no disclosures in the art prior to our invention herein with respect to the utilization of the encapsulating ability of a dendrimer-based network, particularly wherein the dendrimer is a silicon-containing dendrimer based material. Such an invention would be unique for the reason that all known exclusively pure dendrimers are either viscous liquids or amorphous solids.
In contrast, our invention relates to what is believed to be the first dendrimer-based elastomer or plastomer prepared from a radially layered copoly(amidoamine-organosilicon) (PAMAMOS) dendrimer, or from a radially layered copoly(propyleneimine-organosilicon) (PPIOS) dendrimer, capable of functioning as (i) a nanoscopic sponge for the absorption and the encapsulation of various metal cations, and water soluble organic molecules from their water solutions; and which is capable of functioning as (ii) a nanoscopic reactor for various physical and chemical transformations of such encapsulated guest ions and molecules within their elastomeric or plastomeric network. In either case, the resulting products represent novel nanoscopic organo-inorganic composites which contain organosilicon units as an integral part of their covalently bonded structure.
Products resulting from the modifications herein of these PAMAMOS and PPIOS networks have many unique applications among which are in preparing elastomers, plastomers, coatings, sensors, smart materials, membranes, barriers, O-rings, gaskets, sealants, insulators, conductors, magnetic materials, release surfaces, absorbents, implants, sensors, indicators, and radiation sensitive materials. Additionally, because the formation of PAMAMOS and PPIOS networks can be performed in molds of various configurations and designs, these silicon-containing dendrimer-based network composites can be fabricated into objects of various shapes and sizes. This is a distinct benefit and advantage of our invention over pure dendrimers, which as noted, are viscous liquids or amorphous solids, and which possess no useful mechanical properties usually found for engineering polymeric materials.